1. Field of the Disclosure
The present disclosure relates to an optical device which reduces speckle noise of coherent light, and a projection video display device which includes this optical device.
2. Background Art
A projection video display device which causes a light source to emit coherent light (e.g. laser light) and projects and displays a video image produces a spot pattern which is called speckle noise in a display video image.
Unexamined Japanese Patent Publication No. 2008-122823 (Patent Literature 1) discloses a projector. This projector has a movable diffuser on an optical axis of laser light emitted from a light source. The diffuser is rotated or vibrated to reduce speckle noise.
Unexamined Japanese Patent Publication No. 2012-042742 (Patent Literature 2) discloses an optical device. This optical device includes an optical element through which laser light passes. Further, this optical element vibrates in a plane orthogonal to an optical path of laser light to reduce speckle noise.